Electronic devices continue to shrink in size, yet increase in speed and complexity. This has lead to the widespread availability of small electronic components capable of driving high-speed signals (e.g., above one GHz) over printed circuit board (PCB) tracks. The increasing use of these high-speed components has created a significant demand for high performance electrical connectors that support such signal frequencies and denser PCB track configurations, while at the same time requiring less space.
Transmitting high speed signals over differential pair channels is an increasingly popular technique for high bandwidth transmission between PCBs. In a typical high bandwidth system, “daughter card” PCBs are connected to a backplane using mated connectors. The backplane is itself a layered circuit board having, among other things, differential pair tracks formed therein for carrying high frequency signals between the daughter cards.
In such systems, one critical variable that affects bandwidth between PCBs is crosstalk. Generally, crosstalk is the electrical interference in a channel caused by a signal traveling through a neighboring channel. Under many circumstances, the presence of excessive crosstalk degrades system performance and negatively impacts bandwidth. High-speed signaling standards, such the Institute of Electrical and Electronics Engineers (IEEE) 802.3 XAUI standard require four channels of differential pairs operating at 3.125 GHz. Additional high-speed standards incorporating differential pairs include PCI Express, SONET OC-12, SONET OC-48, Gigabit Ethernet, HD-SDI, Serial RapidIO, CEI-6G and SerialLite II. Proprietary protocols are also often implemented in backplanes and other environments.
Using conventional connector technology, it is difficult or impossible to reliably transmit multiple channels of differential signals in close proximity to one another at high speed. The data rates of computing equipment, such as networking gear, have been consistently increasing in speed. As data rates increase, crosstalk between channels becomes more of a problem as it tends to degrade bandwidth. Thus, in differential pair systems, it is important that daughter cards and backplanes minimize the amount of crosstalk between differential pairs. It is also important for the PCB connectors between the daughter cards and backplanes to minimize crosstalk.
In view of the foregoing, there is a substantial need for an electrical connector that yields reduced crosstalk in high signal density, high bandwidth applications.